This article is the first in a series from the Post-Truth Initiative, a Strategic Research Excellence Initiative at the University of Sydney. The series examines today's post-truth problem in public discourse: the thriving economy of lies, bullshit and propaganda that threatens rational discourse and policy.

The project brings together scholars of media and communications, government and international relations, physics, philosophy, linguistics, and medicine, and is affiliated with the Sydney Social Sciences and Humanities Advanced Research Centre (SSSHARC), the Sydney Environment Institute and the Sydney Democracy Network.

Lies, bullshit, propaganda and conspiracy theories show no signs of going away soon, yet post-truth discourse may be one of the most pressing problems of our time. Humans have the capacity to wield unprecedented forms of power, not just over other people, as in acts of law and war, but over other forms of life, and ultimately over the environment that affords our own stability and survival.

If we want to make good decisions, those decisions had better be based on reality, and not on delusion, fantasy, or falsehood. Weakening the link between evidence and decisions not only threatens the quality of policymaking, it threatens the entire enterprise of scientific research, whose business is to find out the facts such that we may make well-informed decisions.

What exactly is post-truth discourse? How and why is it happening? And what can or should we do about it?

Beneath simple labels like post-truth, alternative facts and fake news, there is a complex set of issues. Any debate about the post-truth problem needs some common co-ordinates. Following are seven key reference points.

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1. When we talk about facts, we are talking about statements

A fact is something that can be communicated in the form of a statement, where that statement happens to be true. Before you raise deep philosophical questions of what is truth, just think of everyday cases that present little challenge to our intuitions.

Suppose you reach for a bottle of water to quench your thirst, and I warn you: "That's vodka!" It should not be hard to find out if my statement is true: just sip it and see. Many other statements are straightforward in this way: for example, My house is number 9 on my street; I have two thumbs; ice melts in the summer sun.

Not all claims to fact are easy to verify (like whether a certain foreign leader possesses weapons of mass destruction), and some are probably impossible (like whether ours is the only planet with intelligent life). And facts must be distinguished from opinions, the truth of which cannot be settled independently (like whether chocolate tastes better than vanilla).

But when we talk about facts, we are talking about the statements that describe or assert those facts, and not always the facts themselves. This means that a lot of the time, when people talk about truth, they are focusing on the statements people have made, and not on the facts those statements might describe.

2. Statements are socially constructed

Because we access facts through statements, which are acts of communication, facts are effectively always social in nature. Many scholars say facts are socially constructed. This is true in three ways.

First, facts are always presented in a particular frame. A statement of fact will always come from a person who has chosen to make just this statement and not other statements, and who has chosen to use certain words, and not others, to do it.

Intentionally or not, a person will always emphasise certain things and leave other things in the background. In addition, the language used - whether it is English, Arabic or Zulu - is itself a socially and historically constructed system, with its own in-built patterns of framing and emphasis.

Second, facts are never discovered or described in a cultural or political vacuum. Statements of fact are always a product of their context and time, and of the interests and perspectives of particular people.

Third, there is a specific class of facts that are only true because of human beliefs. An example is "That car belongs to me". This statement of ownership is true only in terms of certain social rights and duties that are created by social institutions.

If I own the car, then, for example, I have the right to decide who can drive it and when, and the duty to pay the fine if caught by a traffic camera.

Many people agree that facts can be socially constructed in at least these ways. But it is important to note that none of these senses threaten the idea that there is a brute reality beyond our statements. No matter how I construct or frame the statement, no matter the language used, or the context of use, ice will melt in the summer sun.

3. Our beliefs are strong but unreliable

For a statement to be a fact it has to be true. Believing that it is true does not make it so. Yet we tend to show great confidence in our beliefs - both when these are based in our first-hand experience, and when these are based on what others say, as long as we trust or identify with those others. But even our most confident beliefs may not correspond with reality.

The ways in which we talk about experiences after the fact - for example, during police interviews following a crime - can result in inaccurate or false memories. Whether by accident or intention, the mere suggestion that a particular event might have happened can result in a person firmly believing that it is true.

Another common source of false beliefs comes from our flawed human patterns of reasoning. Human cognition is not a paragon of cool reason. For example, a confirmation bias in human reasoning leads us to readily accept evidence that supports our beliefs, and yet reject or ignore equally good evidence that goes against it. Many other biases can lead us to embrace beliefs that are false, and thus in turn to make false statements.

4. Not all untruths are lies

Kellyanne Conway at the White House. REUTERS/Kevin Lamarque Telling the truth is usually a simple matter. We have a belief, then we use words to convey that belief to someone else: for example, it's vodka in the bottle, not water.

If our belief is true (it really is vodka), then our statement is true. If our belief is mistaken (it's actually just water), then we are saying something that is false, but this is not the same as lying or bullshitting.

These distinctions show people can make false statements for a range of reasons. The status of any such statement depends on the intentions of the speaker. Do they make the statement in good faith? Do they intend to deceive? Or do they simply not care?

5. Just stating a fact won't make people believe it

White House spokesman Sean Spicer holds a briefing at the White House in Washington, U.S., March 20, 2017. REUTERS/Kevin Lamarque Whatever your motivation, if you want people to accept a statement, then it is not enough that your statements be true. Politicians and PR merchants have long known that what we need is narrative.

The human mind is predisposed to be drawn into stories, and so a message that is clothed in a narrative arc, with a sympathetic protagonist and the tension of action, is more likely to persuade.

While scientists are trained to state the facts, many people observe with dismay the seeming hopelessness of bare statements in the face of compelling stories.

As a result, scientists are cottoning on to the fact that a statement is nothing without a story to drive it. The truth is, facts do not speak for themselves.

6. Statements are reasons

Regardless of whether the speaker is a liar or a bullshitter, a yarn-spinner or simply mistaken, a false statement is a dangerous one. This is because it can then stand as a reason for further actions and statements.

One of the main reasons we make statements at all is to motivate or justify our decisions and actions.

When I say "It's nearly midnight", I am not just stating a fact, I am supplying a reason for action. When I warn you "That's vodka!", I'm not just saying it, I'm giving you a reason not to take a big swig.

Or when the Bush administration stated in 2003 that Saddam Hussein had weapons of mass destruction, they were not just asserting a state of affairs, they were giving a reason why they should invade Iraq. It did stand as a reason, even though later the statement turned out to be false, as many people expected it would be.

By accepting or endorsing a statement, we effectively accept or endorse its consequences. So it is not surprising that the primary goal of making a statement is to get people to accept it, and not necessarily to establish that it is true.

In some settings - for example, in an idealised form of scientific discourse — the way to get people to accept a statement is precisely that: to establish that it is true. But truth is just one possible criterion for accepting statements and their consequences.

Other criteria follow people's cognitive biases and cultural or personal preferences, play on their emotions, or appeal to their identity politics. These are some of the ways in which "alternative facts" are given currency in public discourse today.

When facts are at issue, the stakes are really about what would follow from people accepting a certain statement. This is why we have to take claims to fact seriously; not because truth should be protected in principle, but because we must live with what would follow from treating a statement as valid.

The battle over whether climate change is real is not ultimately about the truth of any given statement. It is a battle over what, if anything, is to be done.

7. Political power can always interfere

Russian President Vladimir Putin plays piano before meeting Chinese leader Xi Jinping on the first day of the Belt and Road Forum in Beijing Thomson Reuters Giving reasons for action can become mere ritual if you happen to have the political power that allows you to do what you want anyway. The most extreme, brazen forms of political power do not bother with giving reasons at all.

But these extreme forms work by means of violence, and violence is based in hard facts. Bullets, shackles and prison walls do their work without any interest in your ideology or beliefs, guilt or innocence.

Political power can be used to suppress or outlaw statements of fact, to remove them from public discourse, and thus to remove their possible consequences from society. Political power can even render certain kinds of facts untrue. Social facts like ownership and membership are based in rights and duties, and can be revoked by those who control social institutions.

But there are limits to what political power can do. As much as we might wish it were possible, suppressing statements of brute fact - that ice melts in the summer sun, for instance - will never stop them from being true.

The quest for answers

The debate about rational discourse continues.

Is the problem new or old? Can we solve it, or are we doomed to grapple with falsity at every turn? Is the problem transformed by the scale of today's communications? Is the solution a political one or a cultural one?

There is much to learn, and much to talk about, but meanwhile my hunch remains: facts will kill us before we kill them.